Microsoft and Twilio will announce on Wednesday that the startup's voice call and messaging libraries for PHP, Java and .NET have been designed to work “flawlessly” with Microsoft’s cloud following work between the pair.

The Windows Azure Developer Center will include detailed documentation on installing these components and using the Twilio API from their Azure apps, director of product management for Twilio Jon Plax told The Reg.

Developers can access the Twilio RESTful APIs from any platform and the company enjoys “good relations” with all platform-as-a-service vendors, Plax said. Interestingly, Twilio draws on the servers of Amazon for its VoIP platform's compute power. However, Plax added: “Windows Azure is the only one where Twilio is a first-class citizen in this way.”

To help drive adoption Twilio will give Windows Azure developers a starting credit equivalent to 1,000 free text messages when they sign up.

As an indication of how important Microsoft is taking this, the Redmond man leading the announcement was Scott Guthrie – the corporate vice president who created Silverlight and was put to work by Microsoft making it easier for coders to actually build apps for Windows Azure.

In a statement, Guthrie said: “We've seen the innovation happening around Twilio, and we want to make it as easy as possible for Windows Azure developers to build great apps that use Twilio's communications platform and take advantage of Windows Azure’s scalability, reliability, and flexibility.”

Twilio was born three years ago and customers include eBay – who dumped Skype on Microsoft for $8.5bn – and Salesforce.com. Skype has integrated Twilio with its StubHub ticketing system - an automated box of tricks that calls sellers and tells them about a pending sale. Salesforce has integrated Twilio with its own Force.com platform.

Twilio claims 75,000 developers are building communications apps using its APIs and it has a mobile client for iOS – thus Windows Azure will boost Apple’s phones and tablets. An Android client is in beta, and there’s nothing so far about a Windows Phone client.

Microsoft has tried to sell Azure as a backend to apps serving mobile devices. But helping both Apple and Amazon as a result reveals just how Microsoft has struggled to gain traction, thanks to tools that are hard for developers to use and customers unwilling to paying for Azure in any meaningful numbers.

Skype, meanwhile, offers SDKs to create clients for Windows, Mac, Android and iPhone while Microsoft has put a version of Skype on Windows Phone. ®